What is the mysterious X-37B space plane? Why was it in orbit for 22 months?

The mission of the unmanned X-37B Orbital Test Vehicle, which is scheduled to touch down at Vandenberg Air Force Base in California today after 22 months in orbit, has been described only vaguely as “to gather more test data.”

The U.S. Air Force’s unmanned X-37B space plane has flown three clandestine missions to date, carrying secret payloads on long-duration flights in Earth orbit.

The robotic vehicle resembles NASA’s famous space shuttle but is much smaller. The X-37B is about 29 feet (8.8 meters) long and 9.5 feet (2.9 m) tall, with a wingspan just less than 15 feet (4.6 m). At launch, it weighs 11,000 lbs. (4,990 kilograms).

And what is the mysterious space plane for? The NPR article examines a number of theories presented by different outlets including space bomber, troop transport vehicle, anti-satellite weapon, and spy plane.

NASA’s Kennedy Space Center in Florida has entered into an agreement with the U.S. Air Force’s X-37B Program for use of the center’s Orbiter Processing Facility (OPF) Bays 1 and 2 to process the X-37B Orbital Test Vehicle for launch.

This agreement ensures the facilities will again be used for their originally-intended purpose — processing spacecraft.

“Kennedy is positioning itself for the future, transitioning to a multi-user launch facility for both commercial and government customers, while embarking on NASA’s new deep space exploration plans,” said Kennedy Center Director Robert Cabana. “A dynamic infrastructure is taking shape, designed to host many kinds of spacecraft and rockets.”